On the basis of the sector-by-sector surveillance, a direction in incidence of a beam of light rays can be determined as being in the range of directions of incidence of the sector most strongly illuminated. Another method is for amplitude values for several sectors to be weighted and the angle of incidence to be determined. The last-mentioned method provides for more accurate determination of the angle of incidence. The operation of the laser warning device is determined by, among others, the antenna. The antenna can be of the sector type, angle type or rotating type. The position of the laser can be determined by sector or angle.
Surveillance of air space with respect to laser light is of greatest importance in order to be able to set up countermeasures against any threat. A laser warning device is therefore used partly in mobile objects such as airplanes, helicopters, armed vehicles and craft, and partly in stationary installations such as, for example, bridges and bunkers.
At present, known laser warning devices of the above type are broad band devices. The broad band width of the laser warning devices implies, at least theoretically, that laser light can be discovered within a wide range of wavelengths. However, broad band laser warning devices are disturbed by various phenomena such as direct or diffuse sunlight, lightning discharges and so forth.